A conventional tension corner fitting for joining a lateral wing box to a centre wing box is shown in FIG. 1. The fitting comprises a base; an end wall meeting the base at a first corner; and a side wall meeting the base at a second corner and the end wall at a third corner. The base and side wall are bolted to one of the wing boxes, and the end wall is bolted to the other.
Such fittings are conventionally formed from a metallic material. It would be desirable to form a fitting of this kind with a composite material, particularly when the centre wing box and/or lateral wing box are also formed from a composite material. This would remove galvanic corrosion and differential thermal expansion between the parts caused by the mismatch in materials. However the different properties of composite materials (in comparison with metals) makes it difficult to form a fitting of the required strength without having to increase the thickness of the walls of the fitting to unacceptable levels. In particular, it would be desirable to increase the thickness of the end wall relative to the base and side wall in order to minimise end wall bending, and to increase the thickness of the corners to minimise through-thickness failure at the corners. This variation in thickness is difficult to manufacture in a composite material, particularly a laminate.